What is the relationship between wet bulb temperature and rain temperature?

[Libertiene]

If the external DBT is 20 deg C and it is 50% RH, then it rains, what temperature is the liquid rain?

I am trying to calculate the heat transfer from a surface when it is raining. I have a set of climate data which will give me external ambient DBT, RH and precipitation. So how can i predict the temperature of the rain water at ground level?

My assumption is that it would be approximately equal to the wet bulb temperature. But I have no idea if this is correct. If rain is formed high in the atmosphere where the temperature is lower how can this be estimated?

It is a bit strange that i can't find a straightforward answer to this question. I have spent ages goggling this and got nowhere. A reference that i can use as justification for an answer would be great.

 

[UltrafastPED]

Try here: http://www.theweatherprediction.com/habyhints/259/

He has discussed several related issues in the starting links.

 

[Libertiene]

Yes but i am not sure how that answers the question. This means that the majority of conventional rain is the "WARM RAIN DROPS" category. This is rain that “is above the current surface temperature". The site gives a way of approximating the wet bulb temperature, but it does not lead me to believe this is also the rain temperature.